Permanent Mold Gravity Casting

Our comprehensive look at the permanent mold gravity casting process will take you through the history as well as the type of products that can be made using this process. We will move on to the casting process as it is in China today, the pros and cons, and the modern day research and developments taking place that puts China on the map for being on of the top developers and producers of casting components and equipment.

A Historical Overview

An age old casting process, permanent mold gravity casting has been revived, improved and further developed to include a broader range of applications in the more recent years gone by.

As suggested by its name, this casting process has two main features:

The use of a mold which is also re-used – the so-called permanent mold

The use of gravity to transfer the molten aluminum from the crucible or furnace to the mold cavity.

Though there is little historic records that documents the development of this process, it is reasonable to assume that it was developed from earlier application processes such as investment casting, but where users sought the option to re-use molds. Taking this into consideration, one can say that this process’s roots extend as far back as 3 200 B.C., or to the early developments of sand casting, which is around the same time.

People’s awareness of this specific process came with the production of lead soldiers – wherein low melting point metals were poured into simple, iron made tools. After the metal in the molds were allowed to set for a few minutes, the mold tool was split and the soldier revealed. Though very simple, this process of making lead soldiers has all the elements of the classic permanent mold process.

Post dating the first production of aluminum in 1852, the development of aluminum permanent mold casting only became a widespread casting adoption some time after this, as aluminum was a scarce and exotic material. Because up a permanent mold casting operation needs a high volume production to justify cost, aluminum casting only became popular during the 1950’s, postdating World War 2. Prior to this time, aluminum casting was large carried out by other processes which included investment casting and sand casting.

Since the Second World War, aluminum permanent mold casting has seen an increasing application in various sectors including that of domestic goods, the defense sector and in the automotive industry (more specifically cars, trucks and motorcycles).

1970 saw the process take a massive leap forward when gravity feed of the molten metal was added to help fill the mould. Assistance for mould filling is provided by either:

Applying a vacuum to help pull the molten material into the mold cavity

The use of positive pressure (in a modified cupola) which helps to push the molten metal into the mold cavity.

This huge development in turn allowed for the development of finer features and larger components and products.

Having a long history, permanent mold gravity die casting still has a bright, diverse developing future.